It is known to mount a metal cutting strip on a carton for cling film so that cling film withdrawn from the carton can be cut on the metal cutting strip. The metal strip may be applied by a machine in which metal sheet from a roll is advanced by passing between driven rollers. The sheet enters a guide which directs the sheet between a fixed lower die and a movable upper die. When the upper die has cut a strip from the sheet, the strip is held onto the die by suction and is carried down onto a carton blank. At the same time as cutting the strip, the strip is perforated by downward pegs which leave downwardly extending teeth around each perforation. The pressure of the upper die forces the teeth into the carton to mechanically fix the metal strip to the carton. The carton blank is brought up to the die and stopped for the cutting strip to be mounted. The conveyor belt for the die is then reversed to move the blank away from the die and bring another blank into position.